This 5-year training program proposes the development plan for a career as an independent biomedical researcher in the area of lung injury and angiogenesis. The principal investigator, has completed Pulmonary and Critical Care Fellowship training through the ABIM Research Pathway. With the sponsors and experienced collaborators he will expand on his scientific skills in preparation for career progression as an independent physician-scientist. The program will emphasize skills in molecular biology of angiogenesis and macrophage regulation of fibrosis using a murine hyperoxia model. To advance his knowledge in computational biology he will attend courses in applied statistics. Steven Greenberg M.D. a macrophage biologist, and Paul Rothman M.D., a renowned immunologist in the area of molecular regulation of cytokine signaling, will provide sponsorship. The program will benefit from collaborative expertise of Jan Kitajewski PhD, an expert in angiogenesis and Patty Lee, M.D. who will provide consultative support for the hyperoxia studies. Additionally, George Yancopoulos, a world renowned investigator, will collaborate and serve with the sponsors, Drs. Kitajewski and Lee on an advisory committee every 8 weeks. This committee will review progress and provide close scientific support and career advice. Prolonged hyperoxia results in lung fibrosis in humans and mice. The accompanying vascular remodeling contributes to pulmonary hypertension, right heart failure, and premature death. This program addresses the questions: Do macrophage-derived angiogenic regulatory factors, particularly angiopoietin-2 (Ang-2), contribute to vascular remodeling in response to prolonged sublethal hyperoxia. Do these vascular alterations contribute, independently, to the development of lung fibrosis? And does macrophage-derived Ang-2 directly inhibit endothelial cell survival in response to hyperoxia? The role of macrophage-derived mediators in hyperoxic lung injury remains unclear. We demonstrate in preliminary experiments, increased Ang-2 mRNA and protein in response to hyperoxic exposure in RAW 264.7 and in a mouse model of sublethal hyperoxic lung fibrosis. These mice develop macrophage-predominant cellular infiltration, collagen deposition and pulmonary vascular regression that recapitulates features of subacute lung fibrosis in humans. The following specific aims will be accomplished: 1) The characterization of fibrotic and vascular remodeling responses in hyperoxia-exposed mice by immuno-histochemistry, Western and Northern blotting and ELISA to quantify changes in markers of lung fibrosis, angiogenesis and expression of angiogenic regulators and their receptors. The effects on pulmonary vasculature will be evaluated by confocal microscopy. 2) Functional changes in response to altered expression of macrophage-derived angiogenic regulators by angiogenesis assays. Macrophage-depleted mice will be used to assess the contribution of lung macrophages. 3) Lung targeted overexpression of Ang-1 or 2 by adenovirus transfection or blocking antibodies prior to hyperoxia to determine the contribution of Ang-2 to pulmonary vascular remodeling and fibrosis during prolonged sublethal hyperoxia. 4) Determine if Ang-2 mediated endothelial survival inhibition is PI3K/Akt dependent. Columbia University has an established record of successful mentorship and training for K08 Career awardees in their preparation for careers as independent.